SPECIFICATIONS FOR BITUMINOUS ROAD MATERIALS. 
51 
rubbing it with a dilute solution of mercuric chloride or nitrate and then with 
mercury. A small quantity of the material to be tested is heated in a metal 
spoon until quite fluid, with care that it suffers no appreciable loss by volatili- 
zation and that it is kept free from air bubbles. It is then poured into the 
collar in a thin stream until slightly more than level with the top. The sur- 
plus may be removed, after the material has cooled to room temperature, by 
means of a spatula or steel knife, which has been slightly heated. The collar 
and plate are then placed in a tin cup containing ice water maintained at 5° C, 
and left in this bath for at least 15 minutes. Meanwhile another cup of 1 
quart capacity is filled about three-fourths full of water and placed on a tripod, 
and the water is heated to the specified temperture at which the test is to be 
made. This temperature should be accurately maintained, and should at no 
time throughout the entire test be allowed to vary more than one-half a degree 
centigrade from the temperature specified. After the material to be tested has 
been kept in the ice water for at least 15 minutes, the collar with its contents 
D 
Fig. 5r — New York Testing Laboratory float apparatus. 
is removed from the plate and screwed into the aluminum float a, which is then 
immediately floated in the warmed bath. As the plug of bituminous material 
becomes warm and fluid, it is gradually forced upward and out of the collar, 
until water gains entrance to the saucer and causes it to sink. 
The time in seconds between placing the apparatus on the water and when 
the water breaks through the bitumen is determined by means of a stop watch, 
and is taken as a measure of the consistency of the material under examination. 
TOTAL BITUMEN. 
[Bulletin 314, p. 25.] 
GOOCH CRUCIBLE METHOD. 
This test consists in dissolving the bitumen in carbon disulphide and recov- 
ering any insoluble matter by filtering the solution through an asbestos felt. 
The form of Gooch crucible best adapted for the determination is 4.4 centi- 
